Previously serprog_rp2040, but we now also support
the RP2530 boards.
Therefore, serprog_pico is a nice generic name. The
directory on release archives will now be serprog_pico
instead of serprog_rp2040; it will contain serprog images
for both RP2040 and RP2530 devices.
Signed-off-by: Leah Rowe <leah@libreboot.org>